It is a fraction because Vulcan's loss and the potential for loss they have stopped in the past is nothing in the face of destruction on the scale Thor is speaking about but it gives them both, the captain especially, plenty of room to grasp the concept. Something inside of Jim twists hatefully especially at the word half. He can imagine all too easily the sort of despot who would design such a weapon.

Jim's sick to his stomach when he shakes his head. He can't hold back how close to tears Thor's loss brings him.

"And now you have to live with what's left." What good would an apology do in the face of that kind of senseless slaughter? It's offensive to even countenance giving one. Jim Kirk reaches out to clasp his hands around Thor's filthy one. He understands, more than anyone should. "Let us help see to you and your friends."

He can't just do nothing after hearing this.